Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include<bits/stdc++.h>
using namespace std;
int n, m, wh, ans, dx[] = {0, 0, 1, -1}, dy[] = {1, -1, 0, 0};
char s[55][55];
struct P{int x, y, c;};
queue<P> qu;

int main(){
	scanf("%d %d\n", &n, &m);
	for(int i = 1; i <= n; i++){
		scanf("%s", s[i]+1);
		for(int j = 1; j <= m; j++) if(s[i][j] == '.') wh++;
	}
	if(s[1][1] == '.') qu.push((P){1, 1, 1});
	while(!qu.empty()){
		P tmp = qu.front(); qu.pop();
		if(tmp.x == n && tmp.y == m) ans = tmp.c;
		for(int i = 0; i < 4; i++) {
			int x = tmp.x + dx[i], y = tmp.y + dy[i];
			if(s[x][y] == '.'){
				qu.push((P){x, y, tmp.c+1});
				s[x][y] = '#';
			}
		}
	}
	printf("%d\n", ans ? wh - ans : -1);
}